Fuel tank for aircraft



Jan. 15, 1957 Filed April 6. 1953 A. c. BOSWELL 2,777,463

FUEL TANK FOR AIRCRAFT 2 Sheets-Sheet 1 INVENTOR mm, same/ BY M!- WATTORN Y 1957 A. c. BOSWELL FUEL TANK FOR AIRCRAFT 2 Sheets-Sheet 2Filed April 6, 1955 lOe FIG. Ia

FIG. 3

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I FUEL TANK AIRCRAFT Arthur Charles Boswell, Preston, England, assignorto The English Electric CompanyLimited, London, England, a Britishcompany Application April 6, 1953, Serial No. 346,929 Claims priority,application Great Britain April 25, 1952 8 Claims. (Cl. 137-341) Forexample fuel tanks arrange'diin the wings of aircraft usually have ventvalves which issue at regions of the aerofoil of the wing, where theaerodynamic effect of the relative movement of the air causes adepression, the effect of which is to be compensated by the constructionof the vent valve. I

In a fuel tank according to the invention the action of aerodynamicpressure on the valve head of a vent valve is balanced by its action inthe opposite sense on a pressure, responsive means of an eifective areaequivalent to that of the said valve head and mechanically. connected tothe said valve head, the said valve being opened against a resilientbiasing force when the internal pressure of the said tank acting onasecond pressure responsive mfiflns of an effective area different fromthat of the said valve head and mechanically connected to thefsaid valvehead exceeds by a predetermined ,value the static air pressure acting onthe same in the opposite direction.

Assuming pm to be the static air pressure, p to be the depression oflocal pressure below said static pressure,

the aerodynamic pressure is po-p acting on the valve head of an area mAand in the opposite direction on a first pressure responsive means ofthe effective area mB equal to that of the valve head. The internal tankpressure pt acts on the said valve head from inside thersaid tank, andon the second pressure responsive means of the effective area mCdifferent from that of the said valve .head. The said static pressure pacts on both the said pressure responsive means in opposite directions.The

resilient closing force be mS. Then:

that is the difference between the internal pressure prof the fuel tankand the static pressure p0 at which the valve opens is independent ofthe local aerodynamic pressure head, and depends merely on the resilientforce and the respective sizes of the valve head and the second pressureresponsive means.

In order that the invention may be clearly understood and readilycarried into effect, some embodiments thereof will now be describedbyway of example with reference to the accompanying drawings, in which:

Fig. 1 is a sectional sideelevation of one embodiment of a ventvalveforla fuel tank of an aircraft in the closed iti o -Figs. '2 to 4'diagrammatically-show three modifications of this embodiment.

around an inside edge thereof is fixed to the casing 10.

and is sealed thereto by sealing pieces 12b and 12c, A valve head 13 isnormallypressed from outside on tothe seating 12a by acoiled compressionspring 14 arranged between the valve body 13 and a plate 15 secured tothe casing ltl. Theplate l5 has a cut-away portion 15a which providescommunication between thecomparjtment 1% and the air flowing over theaircraft.

7 Compartment 101') is separated'from compartment 10a by the valve head13in the closed position shown, and is in communication with the fueltank surrounding the valve casing through the inlets me which extendaround the circumference of the casing 10. v

A hollow valve spindle 16, having a bore 16a extending lengthwisetherethrough, extends longitudinally along the axis of the casing itthrough a -valve guide 12d supported on an arm 12a of the cup 12. I Adiaphragm 17 has its inner portion 'clamped between a conical shoulderon the spindle 16, and an inner conical surface of a bell shapedferruleltS screwed on to the spindle 16.

The .outer portion, of the diaphragm1'7 is secured between a Washer 19and the casing 10. The diaphragm n? thus seals oil the compartment 10])fromwthe compartment iiic. A pair of dish-shaped plates 20 and 22 issecured to the inner end of the spindle 16, and a second diaphragm 21has its inner portion secured between the dish-shaped plates 2 0.and 22,and has'its outeredge secured between a lid Z3and the casing ill. Hencethe diaphragms 2i and the 'plat'esQZtl and 22 seal off the compartmentfrom a compartment 23a formed inside thelid- 23. Thecompartme'nt 23a'isin communication with the compartment 'llia through the bore 16a. .Anair conducting pipe (not shown) is connected with a socket 23-b of thelid 23 and is in communication with a part of the aeroplane known to beat static atmospheric pressure, and with the compartment 16c through anoutlet Jill An electrical heating element 125 is accommodated within aspace 12, formed betweenfthe 'cup 12' and the casing it) and is madeliquid and gas tight by the sealing pieces 12b and 120. Leads 126 fromthe element 125 pass through an opening 10g. in the casing 10 and passthrough a sealing gland 124m an electrical power supply (not shown).

in operation, when the pressure of gases or vapours .above the fuel in.the 'fuel tank and thusin the oom- .partment 10b exceeds thepressure-in the compartment 60 the spring 14 moves the valve head 13 soas to press it on to the seating 12a again.

' In order that the dynamicpressure of air surrounding the aircraftprevailing in the' c'ompartment we shall not move the valve from theclosed position, the effective area of the valve head 13 should be equalto the'effective area of the diaphragm 2i, i. e'. the diameter AA shouldsubstantially equal the diameterB-JB. i

Also the effective area of the diaphragm' l7 should-be less and ispreferably very much less than that "of the diaphragm-21, i.' egin Fig.1 the diameter C-C should be. less than the' diametenA- A or thediameter B -B.

The bore 16a should be of a suitable cross section to partment allow.air to pas freely between the compartments a and 231i without unduerestriction.

The compartments 10a and 23a may be kept in communication with oneanother, in place of by means of the bore 16a, by means of a bore in thewall or of. an air conducting 'pipe outside the casing 10. Alternativelythe compart nnt 23a may be connected by a pipe to the sk'inof theaeroplane, so as tobe in direct communication with the air flowing pastthe aircraft.

I A three-way cock 24 is attached to the socket 2312 which has threepositions: a first position in which it connects the space 10c throughpipe 25a to a point of the aircraft known to be under static airpressure; a second position in which it connects said space 160 to anexternal pressure source through a pipe 25b and reduction valve 26applying a pressure moderately ex ceedibg static air pressure to space100 so as to provide a. pneumatic, resilient biasing force in thedirection of closing thevalve head 13, in which case spring 14 may bedispensedfwith; and a third position in which it connests the said space10c through a pipe 250 to an external pressure source of highpressurelocking the said valve head in the closed position, e. g. in invertedflight so as to prevent loss of fuel through the vent valve.

Referring now to Fig. 2 the valve head 13 opens inwardly, and thediaphragm 17 is of a larger effective area than the said valve head 13'and the diaphragm 21 of an effective area equal to that of the valvehead 13'. The aerodynamic pressure acting at equal force in oppositedirections on the valve head 13' and the diaphragm 21' cancels itselfout. The valve head 13 will openinwardly towards the interior of thetank when the difference between internal pressure and static airpressure acting on the difference between the larger effective area ofdiaphragm 17 and the smaller effective area of diaphragm 21' and of thevalve head 13' exceeds the closing force of a resilient biasing means14'.

Referring now to Figs. 3 and 4:

In Fig. 3 compartments 10a and 10d" are exposed to the internalpressure, compartment 10b" to aerodynamic pressure and compartment 10c"to static pressure; the valve head 13" opens outwardly into thecompartment 10b" and the diaphragm 21" is of a smaller effective areathan the said valve head 13" and the diaphragm 17" which is of equaleffective area to that of the valve head 13'. The aerodynamic pressureacting at equal force in opposite directions on the valve head 13" andthe diaphragm 17 cancels itself out. The valve head 13 will openoutwardly towards the com- 100' in communication with aerodynamicpressure when the difference between internal pressure and. static'air.pressure acting on the difference between the larger effective areas ofdiaphragm 17" and valve headlS" and the smaller effective area ofdiaphragm 21 exceeds the closing force ofa resilient biasing means 14".

In Fig. 4 compartments 10a and 10d" are exposed to the internalpressure, compartment 1011" to aerodynamic pressureand compartment 10c'to static pressure. The valve head 13 opens inwardly into thecompartment 10 a and the diaphragm 21 is of a larger effective area thanthe said ,valve head 13" and the diaphragm 17 which is of equaleffective area to that of the valve head 13". The aerodynamic pressureacting at equal force in opposite directions on the valve head 13' andthe diaphragm 17" cancels itself out. The valve head 13" will openinwardly towards the interior of the tank when the difference betweeninternal pressure and static air pressure acting on the differencebetween the larger effective area of diaphragm 21" and the smallereffective areas of diaphragm 17" and valve head 13" exceeds the closingforce of the resilient biasing means 14".

Fig. la shows a modified detail of the embodiment of the vent valveshown in Fig. l: the simple compression spring 14 of this embodiment ishere replaced by a compound compensating spring arrangement consistingof two compression springs 14' and 14", each fitted round a telescopicbolt 27 linked at one endat 28to the valve head 13', and at the otherend at 29 to the casing 10 within the recess 1011, the said telescopicbolts 27 being arranged diagonally outward from the valve head 13' tothe casing 10.

The arrangement of all the embodiments of the valve may be reversed whenit is desired to keep the pressure Within the container a predeterminedamount below the immediately surrounding pressure (instead of above saidpressure as described hereinabove), for example below the aerodynamicpressure outside a wing tank of an aircraft. In this case the diameterC--C in Figs. 1 and 3 has to be made larger than the diameter A-A, andconversely, the diameter CC in Figs. 2 and 4 has to be made smaller thanthe diameter AA.

While I have described and illustrated what may be considered a typicaland particularaly useful embodiment of my said invention I wish it to beunderstood that i do not limit myself to the particular details anddimensions described and illustrated, for obvious modifications willoccur to' a person skilled in the art.

What I claim as my invention and desire to secure by Letters Patent is:

1. An aircraft fuel tank. comprising in combination: a tank, a valvecasing fitted into the said tank, and having a valve seat, a valve headseated on the said seat and controlling thereby a vent passage from theinterior of the said tank through the said seat to the ambientatmosphere, the space on one side of the said valve head being inoperation in fluid communication with air under aerodynamic pressure andthe space on the other side of the said valve head being in fluidcommunication with the interior of the said tank; first pressureresponsive means located in the said casing and of an effective areaequivalent to that of the said valve head mechanically connectedtherewith, the space in the said casing on one side 0| the said firstpressure responsive means being in operation in fluid communication withair under aerodynamic pressure in the opposite direction and cancellingout the action of the latter on the said valve head, and the space inthe said casing on the other side of the said first pressure rcsponsivemeans being in fluid communication with air under static air pressureacting on the said first pressure responsive means in the oppositedirection of the action of the aerodynamic pressure on the same, secondpressure responsive means located in the said casing and of an effectivearea different from that of the said valve head. the space in the saidcasing on one side of the said second pressure responsive means being influid communication with the interior of the said tank and the space inthe said casing on the other side of the said second pressure responsivemeans being in fluid communication with air under static pressure actingin the opposite direction of the action of the static pressure on thesaid second pressure responsive means, the latter being thus controlledby the difference between the pressure in the interior of the said tankand the static air pressure, and resilient means operatively connectedto said valve head and casing and biasing the said valve head on to thesaid seat.

2. A fuel tank as claimed in claim I comprising in addition: electricalheating means arranged in the said casing adjacent the said valve head.

3. An aircraft fuel tank having a vent valve, opening outwardly from theinterior of the said tank to the ambient atmosphere, comprising incombination: a tank, a valve casing fitted into the said tank and havinga valve seat, a valve head seated on and resiliently biased against thesaid seat from outside, and controlling a vent passage frorn theinterior of the said tank through the said seat to the ambientatmosphere, the space of the said casing outside with respect to saidvalve head being in operation in fluid communication with air underaerodynamic pressure, and the space in the said casing inside withrespect to said valve head being in fluid communication with theinterior of the said tank; a first diaphragm of an effective areadifferent from, and a second diaphragm of an effective area equal to thesaid valve head, both the said diaphragms being mechanically connectedat their centers to the said valve head and at their perimeters to thesaid casing, the space in the said casing at one side of the said firstdiaphragm being in operation in fluid communication with the interior ofthe said tank and exposed to the pressure prevailing therein in thesense of closing the said valve and the space in the said casing at theother side of the said first diaphragm being in operation in fluidcommunication with air under static air pressure acting in the sense of.opening the said valve, and the space in the said casing on one side ofthe said second diaphragm being in operation in fluid communication withair under static air pressure in the sense of closing the said valve,and the space in the said casing on the other side of the said seconddiaphragm being in operation in fluid communication with air underaerodynamic pressure in the opposite sense to the action of the latteron the said valve head.

4. An aircraft fuel tank having a vent valve opening inwardly from theinterior of the said tank to the ambient atmosphere, comprising incombination: a tank, a valve casing fitted into the said tank and havinga valve seat, a valve head seated on and resiliently biased against thesaid seat from inside, and controlling a vent passage from the interiorof the said tank through the said seat to the ambient atmosphere, thespace of the said casing outside with respect to the said Valve headbeing in operation in fluid communication with air under aerodynamicpressure and the space in the said casing inside with respect to thesaid valve head being in fluid communication with the interior of thesaid tank; a first diaphragm of an effective area other than and asecond diaphragm of an effective area equal to that of the said valvehead, both the said diaphragms being mechanically connected at theircenters to the said valve head and at their perimeters to the saidcasing, the space in the said casing at one side of the said firstdiaphragm being in operation in fluid communication with the interior ofsaid tank and exposed to the pressure prevailing therein in the sense ofopening the said valve and the space in the said casing at the otherside of the said first diaphragm being in fluid communication with airunder static pressure acting in the sense of closing the said valve, thespace in said casing at one side of the said second diaphragm being influid communication with air under static pressure acting in the senseof opening the said valve and the space in the said casing at the otherside of the said second diaphragm being in operation in fluidcommunication with air under aerodynamic pressure acting on the saidsecond diaphragm in the opposite direction of its action on the saidvalve head.

5. An aircraft fuel tank, comprising in combination: a tank, a valvecasing fitted into the said tank flush withthe outer surface thereof andhaving a valve seat arranged in a recess which in operation is in openfluid communication with air under aerodynamic pressure, a valve headseated on the said valve seat and controlling thereby a vent passagefrom the interior of the said tank through the said seat to the ambientatmosphere, a compression spring operatively connected to the saidcasing and valve head and biasing the latter on its seat, a valve stemfixedly connected to the said valve head, a first diaphragm of aneffective area other than that of the said valve head fixedly attachedat its center to the said stem and at its perimeter to the said casing,and defining between itself and the said valve head a space in the saidcasing which space is in fluid communication with the interior of thesaid tank, a second diaphragm of an effective area equal to that of thesaid valve head fixedly attached at its center to the said stem and atits perimeter to the said casing and defining between itself and thesaid first diaphragm a 6' space in the said casing which space is influid communication with air under static air pressure, and an inner lidattached to the said casing defining between itself and the said seconddiaphragm a space in the said casing which space is in operation influid communication with the said aerodynamic pressure.

6. A fuel tank as claimed in claim 5, wherein the said stem is hollowand through an aperture in the said valve head forms the said fluidcommunication of the said space in the casing between the said seconddiaphragm and the said inner lid to the air under aerodynamic pressurein the said open recess of the said casing.

7. An aircraft fuel tank, comprising in combination: a tank, a valvecasing fitted into the said tank flush with the outer surface thereof,and having a valve seat arranged in a recess which in operation is inopen fluid communication with air under aerodynamic pressure, a valvehead seated on the said valve seat and controlling thereby a ventpassage from the interior of the said tank through the said seat to theambient atmosphere, a valve stem fixedly connected to said valve head, afirst diaphragm of an effective area other than that of the said valvebody fixedly attached at its center to the said valve head and at itsperimeter to the said casing, and defining between itself and the saidvalve head a space in the said casing which space is' in fluidcommunication with the interior of the said tank, a second diaphragm ofan effective area equal to that of the said valve head fixedly attachedat its center to the said stem and at its perimeter to the said casing,and defining between itself and the said firs-t diaphragm a space in thesaid casing which space is in fluid communication with an externalsource of pneumatic pressure exceeding the static air pressure andproviding a resilient bias in the closing direction of the said valvehead, and an inner lid attached to the said casing and defining betweenitself and the said second diaphragm a space in the said casing whichspace is in operation in fluid communication with air under aerodynamicpressure.

8. An aricraft fuel tank, comprising in combination: a tank, a valvecasing fitted into the said tank and having a valve seat, a valve headseated on and being resiliently biased against said valve seat andthereby controlling a vent passage from the interior of the said tank tothe ambient atmosphere, the space outside with respect to the said valvehead being in fluid communication in operation with air underaerodynamic pressure, a first dia phragm of an effective area smallerthan that of the said valve head and defining between itself and thesaid valve head a space in the said casing in fluid communication withthe interior of the said tank and a second diaphragm of an effectivearea equal to that of the said valve head, both the said diaphragmsbeing mechanically connected at their centers to the said valve head andat their perimeters to the said casing, and defining between one anothera space inside the said casing, switch-over valve means in fluidcommunication with the said space defined between the said twodiaphragms and having one position connecting the last mentioned spaceto air under static air pressure and another position connecting thesame to an external source of pneumatic pressure, and an inner lidattached to the said casing defining between itself and the said seconddiaphragm a space in the said casing which space is in operation influid communication with air under aerodynamic pressure, the saidexternal pneumatic pres sure exceeding both the said static pressure andthe pressure in the tank and locking the said valve head against thesaid seat.

References Cited in the file of this patent UNITED STATES PATENTS2,345,547 Roth et a1 Mar. 28, 1944 2,459,000 Morris Jan. 11, 19492,641,985 Jensen June 16, 1953

